In my co-pending application Ser. No. 542,575, it was pointed out that liquid agricultural sprays were applied to crops in two basic ways. In one manner of application, the liquid chemical sprays were applied to the crops during the tillering stage when the crops were quite small and a conventional ground-type crop sprayer could traverse the field without causing damage to the small plants. However, conventional ground supported crop sprayers are usually not suitable during the latter stages of growth. For example, during the stem extension stage, the likelihood of damage to the standing crops increases if the chemical spray is applied by a ground traversing conventional crop sprayer. Conventional crop sprayers are even more unsuitable for applying liquid agricultural sprays during the heading and ripening stage of the crop.
However, in order to obtain a good yield, it is often necessary to apply chemical spray, for example, a fungicide, during the heading and ripening stages of crops, especially wheat, barley, and the like. Spraying at these latter stages of growth has been typically done by aerial spraying in order to avoid damage to the standing crop. The effectiveness of aerial spraying is dependent in large part upon the weather conditions and, even then, the application of the liquid spray is not as effective as ground spraying if damage to the standing crop can be avoided. Further, the liquid spray must be concentrated when applied by crop dusting because of the limitations of the capacity of the airplane.